In order to expand upon the clinical utility of bone replacement materials, Cambridge Scientific, Inc proposes to develop a biodegradable bone graft extender that has the ability to increase the working volume of autograft without compromising its inductive capacity of autograft Biodegradable extenders would be useful in situations in which autografts are preferable, yet the patient's own bone stocks are deficient. This grant application has as its goal the preclinical development of a degradable poly(propylene glycol-co-fumaric acid) ("PPF")-based bone graft extender containing osteoconductive hydroxylapatite fillers that can be mixed with osteoinductive cancellous autologous bone graft prior to implantation into a bony defect. In the Phase I SBIR feasibility project, Cambridge Scientific, Inc demonstrated in a small animal model that the addition of a PPF-based bone replacement material to autograft bone enhances osteointegratior of autograft which, in turn, has an effect on bony ingrowth. Following this demonstration of PPF/autograft enhancement of new bone formation, Cambridge Scientific, Inc will, in Phase II, evaluate the use of the extender material in a large animal (sheep) defect model to address the eventual clinical use of the extender in the reconstruction of significant skeletal defects. The development of new bone should couple to implant degradation in such a way that the structural integrity of the defect site is maintained throughout the recovery process Osteoinductive autograft material used in conjunction with an osteoconductive and mechanically stable resorbable scaffold would be attractive for both induction and expansion of new bone formation.